854 Appendix Ji From a study of pp. 4.38 to 442 it will be seen that the Bm curve is simply the surn of the shear curve, the point of origin of the former being where Bm = o, viz., at the supports of a girder, and the outer end of a cantilever. E^ will be a maximum where shear changes sign, and will decrease with minus shear. In Fig. 816 let Bm increase by 1000 ton-feet over a base of i foot, caused by a shear of 1000 tons intensity over i foot base; and let a Bm scale of -Jin. = 1000 ton-feet be proposed. Then ^'= 1000 t.f. = -j in., b' = i in., y' 1000 tons § in. x TO, and 10 i = 5m- The Bm curve can now be drawn, on base N P, by sunimatmg D L E K F from pole or Commencing at P, the curve rises to Q £Ot/v/»/vc'V /A/ the maximum, and then decreases from Q to N, the shear being minus. These constructions are especially useful for ships. A curve of weights being drawn, is opposed by a curve of buoyancy or the weight of water displaced at every section, and the net result is the load curve, from which shear and Btt may be deduced as before. Two extreme cases are taken, one with wave crest amidships, causing 'hogging' strains; and the other with crests near the ship ends, causing * sagging' strains. Lastly the sections are treated as built up beams. Fig. 817 is an actual example.